Blood apheresis systems withdraw blood from a donor/patient and separate the blood into various blood components (e.g., red blood cells, white blood cells, platelets, plasma). Some of these blood components are collected and others are returned to the donor/patient.
In many apheresis systems, blood is withdrawn from the donor/patient through a blood inlet line by a blood inlet pump. Anticoagulant (hereinafter sometimes referred to as "AC") is introduced into the blood inlet line at a location which is between the donor/patient and the blood inlet pump. The amount of anticoagulant provided to the blood is important. Introducing less than the desired amount of anticoagulant increases the potential for blood clotting which may adversely affect the apheresis procedure and more importantly the donor/patient. Reductions in the flow of anticoagulant into the blood may be due to an occlusion in the AC inlet line (the line which caries AC to the blood inlet line).
A number of approaches are available to identify occlusions in the flow circuit of a blood apheresis system. Some blood apheresis systems use an electronic drip counter or bag weighing system to control the flow of anticoagulant into the blood. In this case an occlusion in the AC line would be "displayed" to the operator in the nature of there being less "drips" of anticoagulant than normal. Other systems use a pressure sensor in the blood inlet line between the donor/patient and the blood inlet pump to detect for a collapsing of the vein of the donor/patient. Cost considerations are of course always an issue in determining which approach to take for occlusion monitoring in the flow circuit of a blood apheresis system, as increasing the overall cost of the blood apheresis system may have a significant effect on its commercial success.